I have two copies of the base game and was curious if there were any other Overlord scenarios that were playable other than the one included in the box? I do not have access to any of the expansions at this time.

From the offical overloard scenarios there are 4 that only need 2 base games (5 if you swap out the russian army for the US one in Prokhorovka) The 4 are:
Omaha beach overlord
Sward beach overlord
Bastogne overlord
Moyland wood overlord

Then there are a heap from the fan archive which you will just need to search through.